1. Field of the Invention
The present invention relates to multi-mode testing tools which are operable in several modes such as a drill-pipe tester, formation tester, circulation valve and displacement valve.
2. Description of the Related Art
In oil and gas wells, it is common to conduct well testing and stimulation operations to determine production potential and enhance that potential. Annulus pressure responsive downhole tools have been developed which operate responsive to pressure changes in the annulus between the testing string and the well bore casing and can sample formation fluids for testing or circulating fluids therethrough. These tools typically incorporate both a ball valve and lateral circulation ports. Both the ball valve and circulation ports are operable between open and closed positions. A tool of this type is described in U.S. Pat. No. 4,633,952 issued to Ringgenberg and assigned to Halliburton Company. A commercially available multi-mode testing tool of this type is the "Omni SandGuard IV Circulating Valve". The tool is capable of performing in different modes of operation as a drill pipe tester valve, a circulation valve and a formation tester valve, as well as providing its operator with the ability to displace fluids in the pipe string above the tool with nitrogen or another gas prior to testing or retesting. A popular method of employing the circulating valve is to dispose it within a well bore and maintain it in a well test position during flow periods with the ball valve open and the circulation ports closed. At the conclusion of the flow periods, the tool is moved to a circulating position with the ports open and the valve closed. The tool is operated by a ball and slot type ratchet mechanism which provides opening and closing of the valve responsive to a series of annulus pressure increases and decreases. Unfortunately, the changing between ,tool modes in the present tool is limited in that the ratchet dictates preprogrammed steps for changing the tool between its different positions. An operator must follow each of the preprogrammed steps to move the tool between positions. A standard circulating valve ratchet, for instance, requires 15 cycles of pressurization and depressurization in the annulus to move the tool out of the well test position, into the circulating position and back again. This process requires approximately one hour.
It would be desirable, therefore, to employ a tool which will allow an operator to shift the tool from a well test position to a circulating position with a minimum of pressure cycles. An operator would be able to maintain his tool in the well test position and close the tool when desired without following a preprogrammed cycle schedule. The number and times of closures could be orchestrated in accordance with programs established by reservoir engineers or supervisors.